Scientists find Earth-sized world in life-friendly orbit
[A] planet of this size and in the habitable zone is capable of supporting life as we know it," lead researcher Elisa Quintana of NASA's Ames Research Center said at a news conference.
[But] "Don't take off your breathing mask if you ever land there," said Lisa Kaltenegger, a Harvard and Max Planck Institute astronomer who had no connection to the research.
Scientists cannot say for certain whether it has an atmosphere, but if it does, it probably contains a lot of carbon dioxide, outside experts said.
The planet probably basks in an orange-red glow from its star and is most likely cooler than Earth, with an average temperature slightly above freezing, "similar to [a perpetual] dawn or dusk on a spring day," Marcy said.